In the course of testing for and troubleshooting potential fault conditions on a telephone circuit, it is often necessary for a craftsperson to conduct prescribed call establishment and/or call back routines. Although currently available automatic test equipment provides for a limited amount of testing, callback testing typically involves the participation of plural technicians, one of whom is located and places an initial call from a point-of-test remote relative to a central office (such as from a customer premises), and another of whom is typically located at the central office. This multiple participant requirement is especially paramount when testing more recently developed custom calling features, such as call waiting, call forwarding and caller ID for call waiting (deluxe call waiting).
In order to test the operability of these more sophisticated classes of service, such as deluxe call waiting, not only is it is necessary for the craftsperson to prove that multiple incoming and outgoing phone calls are being properly managed, but the technician must ascertain that the phone calls are properly delivered. Making this determination can be tedious and under fault conditions, test requirements are exacerbated by the fact that they may need to be performed repeatedly during the service call, as the technician localizes the cause of the fault. It is readily apparent therefore that, in order to keep pace with diverse products of a continually expanding industry, telephone system service personnel will have to employ automated systems.
One type of automated test device that has proven particularly useful is a telephone ringback test device, of the type described, for example, in the U.S. Pat. No. 4,764,949 issued Aug. 18, 1988 to Richard Faith, et al. (hereinafter referred to as the '949 patent), assigned to the assignee hereof, and the disclosure of which is incorporated herein. The ringback test device of the '949 patent, termed a single access service system (SASS), is designed to remedy the fact that a caller, such as a craftsperson working on the line with a butt-in test set, or a telephone equipment installer, for example, may not know the telephone number associated with the line from which the call to the central office facility is being placed.
The SASS effectively obviates this problem by analyzing prescribed AC and DC signaling characteristics of the calling party's line, when the technician calls into the SASS using a prescribed ringback access code. In response to this code, the SASS signals a specialized trunk (a toll trunk or an outgoing trunk) within the telephone central office, causing it to transmit a message that identifies the caller's telephone number. This number is then stored at the SASS and the technician is instructed to disconnect from the circuit (go back on-hook). Once the technician goes back on-hook, the SASS signals the central office switch, instructing the switch to dial the stored telephone number. If the caller's telephone rings, the ringback test is considered successful.
Now although the SASS is capable of performing ringback testing, as described above, it does not address the testing of recent caller identification-related additions to the CLASS feature set--most notably `Caller Identification with Call Waiting` (CIDCW). CIDCW is defined in Bellcore document TA-NWT-000575 and may be summarized as follows. If a subscriber who is engaged in an active telephone call has the CIDCW feature enabled, and receives an additional incoming call, the subscriber will receive a subscriber-alerting-signal identical to the standard call-waiting tone. Following this initial alerting signal, the subscriber's phone set or other customer premises equipment (CPE) will receive a CPE Alerting Signal (CAS) from the central office switching equipment using the above-referenced Signaling System 7 (SS7) network. This CAS signal prepares the CPE device, such as a Caller ID desk top display unit or display telephone, to receive the Caller ID data associated with the second caller. If the CPE is working properly and ready to receive the Caller ID information, it will respond to the central office switching equipment with an acknowledgement signal, after which the switching equipment will transmit the Caller ID information in accordance with the industry standard format described in Bellcore document TA-NWT-000030.
As pointed out above, the SASS is operative to instruct the calling technician to disconnect from the circuit (go back on-hook), so that the SASS may signal the central office switch, to dial the stored telephone number. However, instructing the calling technician to go on-hook effectively defeats the purpose of testing CIDCW, since this class of service feature is exercised when the called party is already off-hook or busy. As a consequence, current procedures for testing CIDCW require an answering technician at the central office to keep his line off-hook, go to another phone and call back the calling technician, whose incoming line is busy by the mutual off-hook condition of the terminating ends of the original call placed to the central office test site. It will be readily appreciated, therefore, that there is a need for an improved automated ringback test scheme that allows exercising CIDCW class of service without requiring participation of additional telephone service personnel.